1. Field of the Invention
This invention relates to apparatus and methods for deploying, utilizing and recovering well tools, particularly downhole production logging equipment, through a flow line in a well. As used herein, the term "TFL tools" refers to well tools that are pumped down into wells through conduits such as flow lines without being suspended or supported from the surface.
2. Description of Related Art
In the past, production logging equipment has typically been deployed in wells by the use of wireline, coiled tubing or production tubing. Such conventional well logging systems and methods of deployment cannot be used satisfactorily in all situations. One such example is in offshore production where wells are drilled in a template on the ocean floor that is located several miles away from the production platform. Another example is in horizontal wells, especially tight-radius wells or those having long lateral extensions. A system is therefore needed that will enable TFL tools such as production logging equipment to be pumped down into a well through a flow line, utilized and recovered without being suspended from the surface.
Devices and methods useful for pumping well tools downhole through well conduits have previously been disclosed, for example, in U.S. Pat. No. 3,957,119. That patent discloses the use of TFL transport or locomotive pistons joined by a stem comprising a series of interconnecting reach rods to a well tool suspended from the pistons below a circulating nipple in the well bore. In the preferred embodiment, a lock mandrel and standing valve suspended from a running tool are lowered into a no-go landing nipple. The apparatus disclosed therein does not, however, provide means adapted to releasably lock a TFL tool string into a preselected profile in a well bore while simultaneously permitting relative axial movement between the stem and locking means during operation of the well tool. When doing production logging with TFL tools, such axial movement would permit data to be logged at several different points in a well bore without repositioning the locking means.
While axial movement of a logging tool within a well bore is often desirable in order to ascertain well conditions at spaced intervals, means are also needed for limiting the rate of travel at each such interval in order to record meaningful data at a given point.